Method for measuring level of muscle relaxation, processing device thereof and instrument for measuring muscle relaxation

ABSTRACT

Disclosed are a method for measuring the level of muscle relaxation, a device thereof and an apparatus for measuring muscle relaxation, and the method respectively obtains the sampled values of the acceleration and angular velocity of the measurement site via an acceleration sensor and an angular velocity sensor or a speed sensor and an angular velocity sensor, in order to calculate the degree of muscle relaxation according to the sampled values of the acceleration and angular velocity. As the calculated results combine the sampled values of the acceleration and angular velocity of the measurement site, the accuracy of the calculated results is higher. Moreover, the measurement combines an acceleration sensor and an angular velocity sensor or a speed sensor and an angular velocity sensor, so that the apparatus for measuring muscle relaxation can be placed in any position of the measurement site without influencing the accuracy of the measured results.

TECHNICAL FIELD

The present application relates to medical devices, and particularly toa method for measuring the level of muscle relaxation, a processingdevice thereof and an apparatus for measuring muscle relaxation.

BACKGROUND

A patient may generate unexpected movement during surgical proceedingsor may be required to relax his/her muscles to a certain degree.Therefore, a drug such as a muscle relaxant needs to be injected intothe patient. After injection of the drug, monitoring muscle relaxationis usually performed on the patient to evaluate the degree of musclerelaxation. The degree of muscle relaxation can be detected by measuringthe contraction strength of the adductor brevis of the patient's thumb.This is because the contraction strength reflects the degree of musclerelaxation. The strength is proportional to the acceleration accordingto Newton's law. Accordingly, the contraction strength of the adductorbrevis of the thumb can be indirectly obtained by measuring theacceleration generated by movement of the thumb.

The level of muscle relaxation is usually measured by monitoringacceleration values generated by moving the thumb to output accelerationsampled values, and deriving angular velocity values by the accelerationvalues with some motion prediction. However, there exists bias betweenthe motion prediction and actual movement of the thumb, resulting ininaccurate measurement of muscle relaxation. For example, suppose thatthe thumb moves in a circle around a fixed point (e.g., the base of thethumb), then a linear velocity can be acquired by the time integral ofacceleration, and an angular velocity can be computed by dividing thelinear velocity by an estimated length of the thumb. Thus allinformation required by measuring muscle relaxation can be obtained.Obviously, the actual movement of the thumb is not entirely a circularmotion; therefore, such motion prediction may introduce an error in themeasurement result.

SUMMARY

According to a first aspect of the present application, provided is amethod for measuring the level of muscle relaxation, comprising:acquiring acceleration sampled values of a measurement site from anacceleration sensor or a speed sensor, acquiring angular velocitysampled values of the measurement site from an angular velocity sensor,and calculating the level of muscle relaxation according to theacceleration sampled values and the angular velocity sampled values.

According to a second aspect of the present application, provided is aprocessing device for measuring muscle relaxation, comprising: areceiving unit for acquiring acceleration sampled values of ameasurement site from an acceleration sensor or a speed sensor, and foracquiring angular velocity sampled values of the measurement site froman angular velocity sensor; and a processing module for calculating thelevel of muscle relaxation according to the acceleration sampled valuesand the angular velocity sampled values.

According to a third aspect of the present application, provided is anapparatus for measuring muscle relaxation, comprising: aconstant-current source for generating stimulative current and through acurrent output thereof, applying current stimulation on a subject to bedetected; a response-signal extraction end comprising an accelerationsensor and an angular velocity sensor or comprising a speed sensor andan angular velocity sensor; and a processor connected with theconstant-current source for controlling the constant-current source togenerate stimulative current, the processor further communicativelyconnected with the response-signal extraction end for acquiringacceleration sampled values and angular velocity sampled values frommotion information outputted by the response-signal extraction end, andcalculating the level of muscle relaxation according to the accelerationsampled values and the angular velocity sampled values.

In the present application, with an angular velocity sensor, sampledvalues of acceleration and angular velocity of a measurement site can beobtained when detecting the level of muscle relaxation. According to thesampled values of the acceleration and angular velocity, the level ofmuscle relaxation can be computed. Since the computed result associateswith the sampled values of the acceleration and angular velocity of themeasurement site, the accuracy of the computed result is improved.Moreover, the measurement combines an acceleration sensor and an angularvelocity sensor or a speed sensor and an angular velocity sensor toacquire the sampled values of acceleration and angular velocity of themeasurement site, so that an apparatus for measuring muscle relaxationcan be placed in any position of the measurement site withoutinfluencing the accuracy of the measured result.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a schematic view showing measuring the level of musclerelaxation of a thumb with an apparatus for measuring muscle relaxationin an embodiment of the present application;

FIG. 1b is a schematically structural view of an apparatus for measuringmuscle relaxation in an embodiment of the present application;

FIG. 2 is a flowchart of a method for measuring the level of musclerelaxation in an embodiment of the present application;

FIG. 3a is a coordination system in which an acceleration sensor and anangular velocity sensor lie in an embodiment of the present application;

FIG. 3b is a reference coordinate system obtained by rotating acoordination system in which the acceleration sensor lies in FIG. 3 a;

FIG. 4 is a schematic view showing modules of a processing device formeasuring the level of muscle relaxation in an embodiment of the presentapplication.

DETAILED DESCRIPTION

The present application will be further described by the followingdetailed description of specific embodiments with the accompanyingdrawings.

First Embodiment

Please refer to FIG. 1a and FIG. 1b , which show an apparatus formeasuring muscle relaxation in this embodiment that includes a processor201, a constant-current source 202 and a response-signal extraction end203.

The processor 201 is connected with the constant-current source 202 forcontrolling the constant-current source 202 to generate stimulativecurrent. When measuring, a current output of the constant-current source202 is connected to two electrodes via a pair of cables respectively.The two electrodes can be attached to a part of a person being measured.As shown in FIG. 1a , the two electrodes are attached to a wrist of theperson being measured, and the response-signal extraction end 203 isattached to a thumb of the person being measured. When theconstant-current source 202 outputs stimulative current, the personbeing measured may get an electric shock at the wrist, and the thumb maybe moved due to the stimulation. The response-signal extraction end 203may sense the movement of the thumb and output motion information.

The processor 201 is also communicatively connected with theresponse-signal extraction end 203; exchanges data with theresponse-signal extraction end 203, for example, receiving motioninformation outputted by the response-signal extraction end 203; andcalculates the level of muscle relaxation based on the motioninformation. In another embodiment, the processor 201 may also sendinformation about configuration, calibration and/or identity to theresponse-signal extraction end 203. The communication connectionincludes wired and wireless connection.

In an embodiment, the response-signal extraction end 203 includes anacceleration sensor and an angular velocity sensor. The accelerationsensor refers to a sensor which can sense an acceleration of a subjectto be measured and convert the acceleration into electrical signals foroutputting. The angular velocity sensor refers to a sensor which cansense an angular velocity of the subject to be measured and convert theangular velocity into electrical signals for outputting. In the firstembodiment, the acceleration sensor can output real-time accelerationinformation, and the angular velocity sensor can output real-timeangular velocity information. The response-signal extraction end 203transmits the information about acceleration and angular velocity to theprocessor 201. The information about acceleration and angular velocitymay be analog electrical signals, digital signals, continuous waveformdata or discrete sampled values. The processor 201 may acquire sampledvalues of acceleration and angular velocity from the information aboutacceleration and angular velocity, and calculate the level of musclerelaxation based on the sampled values of acceleration and angularvelocity.

In another embodiment, the response-signal extraction end 203 includes aspeed sensor and an angular velocity sensor. The speed sensor refers toa sensor which can sense a kinematic velocity of the subject to bemeasured. The response-signal extraction end 203 can directly outputinformation about velocity and time, or it may calculate accelerationbased on the information about velocity and time, and convert theacceleration into electrical signals for outputting. Accordingly,besides the information about angular velocity, the information acquiredby the processor 201 from the response-signal extraction end 203 mayalso include information about speed or acceleration. When acquiringspeed information from the response-signal extraction end 203, theprocessor 201 can calculate acceleration based on the information aboutspeed and time. Then the processor 201 can calculate the level of musclerelaxation based on the information about acceleration and angularvelocity.

The processor 201 may, according to the sampled values of accelerationand angular velocity, calculate the level of muscle relaxation byadopting a following scheme:

The processor 201 may, according to initial components of gravityacceleration, compute rotation angles from an initial coordinate systemto a reference coordinate system, calculate a transition matrix from theinitial coordinate system to the reference coordinate system based onthe rotation angles, and obtain a transition matrix from the referencecoordinate system to the initial coordinate system based on thetransition matrix from the initial coordinate system to the referencecoordinate system. The reference coordinate system, which corresponds toa transition matrix, may be acquired by converting the coordinate systemin which an initial acceleration lies (i.e., the initial coordinatesystem). Different transition matrixes may correspond to differentreference systems, which can be determined according to the actualsituation. In a simple case, the coordinate system in which the initialacceleration lies is converted so as to make the gravity accelerationappear only a component on a single dimension of the referencecoordinate system and other components thereof on other dimensions arezero, which may simplify further processing.

The processor 201 may analyze the sampled values of the angular velocityto acquire rotation angles along the moving direction of an individualaxis about the measurement site, and calculate motion vectors based onthe rotation angles along the moving direction of an individual axisabout the measurement site. In a specific example, the processor 201 maycalculate the motion vectors with an inertial navigation algorithm whichmay refer to an algorithm like Picord algorithm or multi-sample rotationvector algorithm adopted to solve a pose of an object in motion based ondata measured by an angular velocity sensor like a gyroscope to obtainthe vectors of motion state of the measurement site. The vectors ofmotion state may represent motion information about the part to bemeasured when the part is moving after it is stimulated. According tothe vectors of motion state, a transition matrix from the initialcoordinate system to a kinetic coordinate system can be acquired. Themotion information at least includes information of acceleration orspeed and angular velocity about the measurement site when the part ismoving.

The processor 201 may acquire the initial components of the gravityacceleration in the initial coordinate system at time t₀ with theacceleration sensor or the speed sensor, where the time t₀ may be anytime before giving out an electrical stimulation and the measurementsite staying still; then calculate the transition matrix from thereference coordinate system to the initial coordinate system at the timet₀ based on the initial components of the gravity acceleration; computethe transition matrix from the initial coordinate system to the kineticcoordinate system based on the sampled values of the angular velocity;and acquire the transition matrix from the reference coordinate systemto the kinetic coordinate system according to the transition matrix fromthe reference coordinate system to the initial coordinate system and thetransition matrix from the initial coordinate system to the kineticcoordinate system.

The processor 201 may calculate the transition matrix from the referentcoordinate system to the kinetic coordinate system according to theacceleration sampled values outputted by the acceleration sensor or thespeed sensor and the angular velocity sampled values outputted by theangular velocity sensor at time t_(k), and acquire components of thegravity acceleration in the acceleration sensor coordinate system or thespeed sensor coordinate system according to components of the gravityacceleration projected in the reference coordinate system and thetransition matrix from the reference coordinate system to the kineticcoordinate system, where the time t_(k) may be any time after giving outthe electrical stimulation, the kinetic coordinate system may be theacceleration sensor coordinate system or the speed sensor coordinatesystem at the time t_(k), the components of the gravity acceleration inthe reference coordinate system are [0, 1, 0].

The processor 201 may calculate components of the gravity accelerationin the acceleration sensor or speed sensor coordinate system accordingto the sampled values of acceleration and angular velocity, subtract thecomponents of the gravity acceleration from the acceleration sampledvalues to obtain real acceleration components in the acceleration sensoror speed sensor coordinate system, perform a composition operation onthe real acceleration components to obtain acceleration values generatedby actual movement of the measurement site, and calculate the level ofmuscle relaxation based on the acceleration values.

Since the apparatus for measuring muscle relaxation senses the movementof the measurement site with the acceleration sensor and the angularvelocity sensor to output real-time sampled values of acceleration andangular velocity, and computes the level of muscle relaxation based onthe sampled values of acceleration and angular velocity, the computedresults associate with the sampled values of the acceleration andangular velocity of the measurement site and the influence of gravity iseliminated during the computation, which improves the accuracy of thecomputed results. Moreover, the device for measuring muscle relaxationof the apparatus can be placed in any position of the measurement sitewithout influencing the accuracy of the measured result.

In a specific example, the angular velocity sensor can particularly be agyro sensor.

In this embodiment, the apparatus for measuring muscle relaxationfurther includes a display 204 to which the processor 201 sends thecomputed results of the level of muscle relaxation for display.

The way the processor 201 measures muscle relaxation based on thesampled values of acceleration and angular velocity is by measuring thelevel of muscle relaxation of a thumb with the response-signalextraction end 203 in a three-dimensional coordinate system.

The measuring device of the apparatus for measuring muscle relaxation ismounted at any position on the thumb and has a same kinestate with thethumb, in this case, X_(a), Y_(a), Z_(a) are the three axes of theacceleration sensor coordinate system respectively, and X_(b), Y_(b),Z_(b) are the three axes of the angular velocity sensor coordinatesystem respectively. The subject to be measured is stimulated withelectrical current by the apparatus through the two electrodes connectedon the wrist, and the thumb moves when it is stimulated. Theacceleration sensor and the angular velocity sensor output triaxialacceleration sampled values and triaxial angular velocity sampled valuesrespectively when the thumb is moved. The processor 201 may calculatethe components of the gravity acceleration at the three axes of theacceleration sensor coordinate system according to the triaxialacceleration sampled values and triaxial angular velocity sampledvalues, subtract the components of the gravity acceleration at the threeaxes of the acceleration sensor coordinate system from the triaxialacceleration sampled values to obtain real acceleration components ofthe measurement site, perform a composition operation on the realacceleration component to obtain acceleration values generated by actualmovement of the measurement site, and calculate the level of musclerelaxation based on the acceleration values.

When the measurement site is still, the initial coordinate system of theacceleration sensor is A_(t0) and the reference coordinate system R isobtained by rotating the initial coordinate system A_(t0). In thespecific example, one axis of the reference coordinate system Rcoincides with the direction of the gravity acceleration, for example,as to a three-dimensional coordinate system, the components of thegravity acceleration in the reference coordinate system can be [0, 1,0]. The reference coordinate system R can be obtained by rotating theinitial coordinate system. For example, the reference coordinate systemR can be obtained by rotating the initial coordinate system A_(t0) by anangle φ along z axis then rotating by an angle θ along x axis, where therotation angles are φ=cos⁻¹(y_(A) _(t0) /√{square root over (x_(A) _(t0)²+y_(A) _(t0) ²)}) and θ=sin⁻¹(z_(A) _(t0) /√{square root over (x_(A)_(t0) ²+y_(A) _(t0) ²+z_(A) _(t0) ²)}), A_(A) _(t0) , y_(A) _(t0) ,z_(A) _(t0) are acceleration components sensed by the accelerationsensor along x, y, z axes respectively in the initial coordinate systemA_(t0).

The processor 201 may acquire a transition matrix of the initialcoordinate system A_(t0) around the z axis based on the rotation angleφ:

${C_{Z} = \begin{bmatrix}{\cos\;\varphi} & {\sin\;\varphi} & 0 \\{{- \sin}\;\varphi} & {\cos\;\varphi} & 0 \\0 & 0 & 1\end{bmatrix}},$

The processor 201 may acquire a transition matrix of the initialcoordinate system A_(t0) around the x axis based on the rotation angleθ:

${C_{X}\begin{bmatrix}1 & 0 & 0 \\0 & {\cos\;\theta} & {\sin\;\theta} \\0 & {{- \sin}\;\theta} & {\cos\;\theta}\end{bmatrix}},$

The processor 201 may acquire a transition matrix from the referencecoordinate system R to the initial coordinate system A_(t0) based on thetransition matrixes C_(Z) and C_(X):C _(R) ^(A) ^(t0) =C _(Z) ·C _(X))^(T);

Of course, it can be understood by those skilled in the art that thereference coordinate system R can also be obtained by rotating theinitial coordinate system A_(t0) in other rotation manners; in thiscase, the transition matrixes acquired by rotating the initialcoordinate system A_(t0) around the z, x axes by the processor 201 maybe different from those mentioned above.

When the measurement site is moved by current stimulation, the processor201 performs an integral operation respectively on the triaxial angularvelocity sampled values outputted by the angular velocity sensor toacquire the rotation angles Δθ_(x), Δθ_(y), Δθ_(z) of the measurementsite along triaxial directions, and according to the rotation anglesΔθ_(x), Δθ_(y), Δθ_(z) of the measurement site along triaxialdirections, acquire a quaternion q₀(t_(k)), q₁(t_(k)), q₂(t_(k)),q₃(t_(k)) which can represent motion information about the measurementsite when it moves after it is stimulated. The motion information may atleast include information about acceleration and angular velocity of themeasurement site when it moves. In the embodiment, the processor 201 maycalculate the quaternion of the measurement site in motion with thePicord algorithm.

$\begin{bmatrix}{q_{0}\left( t_{k} \right)} \\{q_{1}\left( t_{k} \right)} \\{q_{2}\left( t_{k} \right)} \\{q_{3}\left( t_{k} \right)}\end{bmatrix} = {\quad{{{\begin{bmatrix}{\cos\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{x}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{y}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{z}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} \\{\frac{\Delta\;\theta_{x}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {\cos\frac{\Delta\;\theta}{2}} & {\frac{\Delta\;\theta_{z}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{y}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} \\{\frac{\Delta\;\theta_{y}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{z}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {\cos\frac{\Delta\;\theta}{2}} & {\frac{\Delta\;\theta_{x}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} \\{\frac{\Delta\;\theta_{z}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {\frac{\Delta\;\theta_{y}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{x}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {\cos\frac{\Delta\;\theta}{2}}\end{bmatrix}\begin{bmatrix}{q_{0}\left( t_{k - 1} \right)} \\{q_{1}\left( t_{k - 1} \right)} \\{q_{2}\left( t_{k - 1} \right)} \\{q_{3}\left( t_{k - 1} \right)}\end{bmatrix}}\mspace{20mu}{where}},\mspace{20mu}{{\Delta\;\theta} = \sqrt{{\Delta\;\theta_{x}^{2}} + {\Delta\;\theta_{y}^{2}} + {\Delta\;\theta_{z}^{2}}}},\mspace{20mu}{\begin{bmatrix}{q_{0}\left( t_{0} \right)} \\{q_{1}\left( t_{0} \right)} \\{q_{2}\left( t_{0} \right)} \\{q_{3}\left( t_{0} \right)}\end{bmatrix} = {\begin{bmatrix}1 \\0 \\0 \\0\end{bmatrix}.}}}}$

Of course, the quaternion of the measurement site in motion can also becalculated with the multi-sample rotation vector algorithm. The Picordalgorithm used to calculate the quaternion by the processor 201 in theembodiment should not be considered to limit the present application.

Then the processor 201 may, according to the acquired quaternion,acquire a transition matrix from the initial coordinate system A_(t0) tothe kinetic coordinate system A_(tk) in which the acceleration sensorlies at any time when the measurement site moves after it is stimulated:

$C_{A_{t_{0}}}^{A_{t_{k}}} = \begin{bmatrix}{{q_{0}\left( t_{k} \right)}^{2} + {q_{1}\left( t_{k} \right)}^{2} - {q_{2}\left( t_{k} \right)}^{2} - {q_{3}\left( t_{k} \right)}^{2}} & {2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}} - {{q_{0}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}}} \right\rbrack} & {2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} + {{q_{0}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}}} \right\rbrack} \\{2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}} + {{q_{0}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}}} \right\rbrack} & {{q_{0}\left( t_{k} \right)}^{2} + {q_{1}\left( t_{k} \right)}^{2} + {q_{2}\left( t_{k} \right)}^{2} - {q_{3}\left( t_{k} \right)}^{2}} & {2\left\lbrack {{{q_{2}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} - {{q_{0}\left( t_{k} \right)}{q_{1}\left( t_{k} \right)}}} \right\rbrack} \\{2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} - {{q_{0}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}}} \right\rbrack} & {2\left\lbrack {{{q_{2}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} + {{q_{0}\left( t_{k} \right)}{q_{1}\left( t_{k} \right)}}} \right\rbrack} & {{q_{0}\left( t_{k} \right)}^{2} - {q_{1}\left( t_{k} \right)}^{2} - {q_{2}\left( t_{k} \right)}^{2} + {q_{3}\left( t_{k} \right)}^{2}}\end{bmatrix}$

The processor 201 may calculate a transition matrix from the referencecoordinate system R to the kinetic coordinate system A_(tk) with anequation C_(R) ^(A) ^(tk) =C_(A) _(t0) ^(A) ^(tk) C_(R) ^(A) ^(t0) .

In this case, the processor 201 may multiply the components of thegravity acceleration projected in the reference coordinate system by thetransition matrix from the reference coordinate system to the kineticcoordinate system to acquire triaxial components of the gravityacceleration in the acceleration sensor coordination system, i.e.,[G_(x), G_(y), G_(z)]^(T)=C_(R) ^(A) ^(tk) [0, 1, 0]^(T), where thecomponents of the gravity acceleration projected in the referencecoordinate system are [0, 1, 0]^(T).

Suppose that the response-signal extraction end 203 lies in aone-dimensional or two-dimensional coordinate system, with the aboveidea, similarly, the influence of gravity acceleration can also beeliminated by coordinate transformation based on sampled values ofacceleration and angular velocity.

In the apparatus for measuring muscle relaxation provided in theembodiment, by means of subtracting the components of the gravityacceleration in the acceleration sensor coordination system from theacceleration sampled values to obtain real acceleration components ofthe measurement site, the influence of the gravity acceleration to themeasured results can be eliminated, which improves the accuracy of themeasurement.

The processor 201 can be one or more integrated chips with recordedprograms which can be performed to achieve the above functions.

Second Embodiment

Please refer to FIG. 2. By taking an example of a three-dimensionalcoordinate system, the method for measuring the level of musclerelaxation provided in this embodiment may include the following steps:

Step 101, when the subject to be measured moves after it is currentstimulated, outputting triaxial acceleration sampled values about thepart being measured by the acceleration sensor.

Step 102, outputting triaxial angular velocity sampled values about thepart being measured by the angular velocity sensor.

Step 103, acquiring triaxial components of the gravity acceleration inthe acceleration sensor coordinate system according to axialacceleration sampled values and axial angular velocity sampled values bythe apparatus.

Step 104, subtracting the triaxial components of the gravityacceleration in the acceleration sensor coordinate system obtained instep 103 from the triaxial acceleration sampled values to obtain realacceleration components of the part being measured by the apparatus.

Step 105, performing a composition operation on the real accelerationcomponents of the part being measured obtained in step 104 to obtain anacceleration value √{square root over (a_(x) ²+a_(y) ²+a_(z) ²)}generated by actual movement of the part being measured, then extractingeffective peak information of the composite acceleration which isregarded as real acceleration generated by the movement of the partbeing measured, taking the real acceleration to calculate the level ofmuscle relaxation, and outputting the calculated results.

In the embodiment, the step 103 where the apparatus acquires triaxialcomponents of the gravity acceleration in the acceleration sensorcoordinate system according to axial sampled values of acceleration andangular velocity may comprise:

Please refer to FIG. 3a , which shows a coordinate system in which theacceleration sensor and the angular velocity sensor lie, where X_(a),Y_(a), Z_(a) represent three axes of the acceleration sensor coordinatesystem, and X_(b), Y_(b), Z_(b) represent three axes of the angularvelocity sensor coordinate system. Please refer to FIG. 3b , which showsa reference coordinate system obtained by rotating the accelerationsensor coordinate system of FIG. 3a , where X_(R), Y_(R), Z_(R)represent three axes of the reference coordinate system R; in thereference coordinate system R, the components of the gravityacceleration at the three axes are [0, 1, 0].

When the part being measured is still, the initial coordinate system ofthe acceleration sensor is A_(t0), the reference coordinate system R isobtained by rotating the initial coordinate system A_(t0), and thecomponents of the gravity acceleration in the reference coordinatesystem can be [0, 1, 0]. Preferably, in the embodiment, the referencecoordinate system R can be obtained by rotating the initial coordinatesystem A_(t0) by an angle φ along the z axis then rotating by an angle θalong the x axis, where the rotation angles are φ=cos⁻¹(y_(A) _(t0)/√{square root over (x_(A) _(t0) ²+y_(A) _(t0) ²)}) and θ=sin⁻¹(z_(A)_(t0) /√{square root over (x_(A) _(t0) ²+y_(A) _(t0) ²+z_(A) _(t0) ²)}),and x_(A) _(t0) , y_(A) _(t0) , z_(A) _(t0) , are accelerationcomponents sensed by the acceleration sensor along the x, y, z axesrespectively in the initial coordinate system A_(t0).

A transition matrix of the initial coordinate system A_(t0) around the zaxis can be acquired based on the rotation angle φ:

${C_{z} = \begin{bmatrix}{\cos\;\varphi} & {\sin\;\varphi} & 0 \\{{- \sin}\;\varphi} & {\cos\;\varphi} & 0 \\0 & 0 & 1\end{bmatrix}},$

A transition matrix of the initial coordinate system A_(t0) around the xaxis can be acquired based on the rotation angle θ:

${C_{X}\begin{bmatrix}1 & 0 & 0 \\0 & {\cos\;\theta} & {\sin\;\theta} \\0 & {{- \sin}\;\theta} & {\cos\;\theta}\end{bmatrix}}.$

A transition matrix from the reference coordinate system R to theinitial coordinate system A_(t0) can be acquired based on the transitionmatrixes C_(Z) and C_(X):C _(R) ^(A) ^(t0) =(C _(Z) ·C _(X))^(T).

Of course, it can be understood by those skilled in the art that thereference coordinate system R can also be obtained by rotating theinitial coordinate system A_(t0) in other rotation manners; in thiscase, the transition matrixes acquired by rotating the initialcoordinate system A_(t0) around the z, x axes may be different fromthose mentioned above.

When the measurement site is moved by current stimulation, the triaxialangular velocity sampled values outputted by the angular velocity sensorare analyzed respectively to acquire the rotation angles Δθ_(x), Δθ_(y),Δθ_(z) of the measurement site along triaxial directions, in theembodiment, the rotation angles of the measurement site along triaxialdirections can be acquired by performing an integral operation, afterwhich, according to the rotation angles Δθ_(x), Δθ_(y), Δθ_(z) of themeasurement site along triaxial directions, the vectors of motion statewhich can represent motion information about the measurement site whenit moves after it is stimulated can be acquired. The motion informationmay at least include information about acceleration and angular velocityof the measurement site in motion. In a specific example, the motionvectors can be a quaternion q₀(t_(k)), q₁(t_(k)), q₂(t_(k)), q₃(t_(k)).In the embodiment, the quaternion of the measurement site in motion canbe calculated by the Picord algorithm:

$\begin{bmatrix}{q_{0}\left( t_{k} \right)} \\{q_{1}\left( t_{k} \right)} \\{q_{2}\left( t_{k} \right)} \\{q_{3}\left( t_{k} \right)}\end{bmatrix} = {\quad{{{\begin{bmatrix}{\cos\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{x}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{y}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{z}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} \\{\frac{\Delta\;\theta_{x}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {\cos\frac{\Delta\;\theta}{2}} & {\frac{\Delta\;\theta_{z}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{y}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} \\{\frac{\Delta\;\theta_{y}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{z}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {\cos\frac{\Delta\;\theta}{2}} & {\frac{\Delta\;\theta_{x}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} \\{\frac{\Delta\;\theta_{z}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {\frac{\Delta\;\theta_{y}}{\Delta\;\theta}\sin\frac{\Delta\;\theta}{2}} & {{- \frac{\Delta\;\theta_{x}}{\Delta\;\theta}}\sin\frac{\Delta\;\theta}{2}} & {\cos\frac{\Delta\;\theta}{2}}\end{bmatrix}\begin{bmatrix}{q_{0}\left( t_{k - 1} \right)} \\{q_{1}\left( t_{k - 1} \right)} \\{q_{2}\left( t_{k - 1} \right)} \\{q_{3}\left( t_{k - 1} \right)}\end{bmatrix}}\mspace{20mu}{where}},\mspace{20mu}{{\Delta\;\theta} = \sqrt{{\Delta\;\theta_{x}^{2}} + {\Delta\;\theta_{y}^{2}} + {\Delta\;\theta_{z}^{2}}}},\mspace{20mu}{\begin{bmatrix}{q_{0}\left( t_{0} \right)} \\{q_{1}\left( t_{0} \right)} \\{q_{2}\left( t_{0} \right)} \\{q_{3}\left( t_{0} \right)}\end{bmatrix} = {\begin{bmatrix}1 \\0 \\0 \\0\end{bmatrix}.}}}}$

Of course, the quaternion of the measurement site in motion can also becalculated with the multi-sample rotation vector algorithm. The Picordalgorithm used to calculate the quaternion in the embodiment should notbe considered to limit the present application.

Then, according to the acquired quaternion, a transition matrix from theinitial coordinate system A_(t0) to the kinetic coordinate system A_(tk)in which the acceleration sensor lies at any time when the measurementsite moves after it is stimulated can be acquired:

$C_{A_{t_{0}}}^{A_{t_{k}}} = \begin{bmatrix}{{q_{0}\left( t_{k} \right)}^{2} + {q_{1}\left( t_{k} \right)}^{2} - {q_{2}\left( t_{k} \right)}^{2} - {q_{3}\left( t_{k} \right)}^{2}} & {2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}} - {{q_{0}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}}} \right\rbrack} & {2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} + {{q_{0}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}}} \right\rbrack} \\{2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}} + {{q_{0}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}}} \right\rbrack} & {{q_{0}\left( t_{k} \right)}^{2} + {q_{1}\left( t_{k} \right)}^{2} + {q_{2}\left( t_{k} \right)}^{2} - {q_{3}\left( t_{k} \right)}^{2}} & {2\left\lbrack {{{q_{2}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} - {{q_{0}\left( t_{k} \right)}{q_{1}\left( t_{k} \right)}}} \right\rbrack} \\{2\left\lbrack {{{q_{1}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} - {{q_{0}\left( t_{k} \right)}{q_{2}\left( t_{k} \right)}}} \right\rbrack} & {2\left\lbrack {{{q_{2}\left( t_{k} \right)}{q_{3}\left( t_{k} \right)}} + {{q_{0}\left( t_{k} \right)}{q_{1}\left( t_{k} \right)}}} \right\rbrack} & {{q_{0}\left( t_{k} \right)}^{2} - {q_{1}\left( t_{k} \right)}^{2} - {q_{2}\left( t_{k} \right)}^{2} + {q_{3}\left( t_{k} \right)}^{2}}\end{bmatrix}$

Then, the transition matrix from the reference coordinate system R tothe kinetic coordinate system A_(tk) can be C_(R) ^(A) ^(tk) =C_(A)_(t0) ^(A) ^(tk) C_(R) ^(A) ^(t0) .

In this case, triaxial components of the gravity acceleration in theacceleration sensor coordination system can be obtained by multiplyingthe components of the gravity acceleration projected in the referencecoordinate system by the transition matrix from the reference coordinatesystem to the kinetic coordinate system, i.e., [G_(x), G_(y),G_(z)]^(T)=C_(R) ^(A) ^(k) [0, 1, 0]^(T), where the components of thegravity acceleration projected in the reference coordinate system are[0, 1, 0]^(T).

In the method for measuring the level of muscle relaxation provided inthe embodiment, the level of muscle relaxation can be calculated bysampled values of acceleration and angular velocity obtained by theacceleration sensor and the angular velocity sensor, and the influenceof the gravity acceleration to the measured result can be eliminatedduring calculation, which can improve the accuracy of the measurement,so that a corresponding measuring device can be placed at any positionof the measurement site without influencing the accuracy of the measuredresult.

Third Embodiment

Please refer to FIG. 4, in which provided in the embodiment is aprocessing device for measuring the level of muscle relaxation whichincludes a processing module 401 and a receiving unit 2011.

When measuring, the processing module 401 is connected with theconstant-current source 202 for controlling the constant-current source202 to generate stimulative current so as to perform electricalstimulation on a subject to be detected through an electrical output ofthe constant-current source 202. The response-signal extraction end 203is placed on the measurement site and has a same kinestate with themeasurement site. When the measurement site moves after it isstimulated, the response-signal extraction end 203 senses and outputsmotion information about the measurement site. The response-signalextraction output end 203 may include an acceleration sensor and anangular velocity sensor, or the response-signal extraction output end203 may include a speed sensor and an angular velocity sensor. In theembodiment, the current output of the constant-current source 202 mayalso be connected with the processing module 401 for feeding back theoutputted current to the processing module 401 for monitoring so as toensure parameters like the outputted current remain within a range whichthe measurement site can tolerate.

The processor 401 may include a gravity acceleration subtraction unit2012, a composition unit 2013 and a muscle relaxation calculation unit2014. The receiving unit 2011 is used for acquiring acceleration sampledvalues of the part being measured from the acceleration sensor andangular velocity sampled values of the part being measured from theangular velocity sensor. The gravity acceleration subtraction unit 2012may include a first subunit and a second subunit, wherein the firstsubunit is configured for calculating components of the gravityacceleration in the acceleration sensor coordinate system based on thesampled values of acceleration and angular velocity, and the secondsubunit is configured for subtracting the components of the gravityacceleration in the acceleration sensor coordinate system to obtain realacceleration components of the part being measured. The composition unit2013 is configured for performing a composition operation on the realacceleration components to obtain an acceleration value √{square rootover (a_(x) ²+a_(y) ²+a_(z) ²)} generated by actual movement of themeasurement site. The muscle relaxation calculation unit 2014 isconfigured for taking the real acceleration to calculate the level ofmuscle relaxation and outputting the calculated results.

In the embodiment, the first subunit of the gravity accelerationsubtraction unit 2012 may calculate a transition matrix from thereference coordinate system to the kinetic coordinate system accordingto the sampled values of acceleration and angular velocity of the partbeing measured obtained from an acceleration sensor and an angularvelocity sensor at time t_(k), and multiply the components of thegravity acceleration projected in the reference coordinate system by thetransition matrix from the reference coordinate system to the kineticcoordinate system to acquire the components of the gravity accelerationin the kinetic coordinate system, where the time t_(k) may be any timeafter giving out the electrical stimulation, the kinetic coordinatesystem may be the coordinate system in which the acceleration sensorlies at the time t_(k), the reference coordinate system is obtained byrotating the initial coordinate system, the projecting components of thegravity acceleration may appear in the reference coordinate system, theinitial coordinate system is a coordinate system in which theacceleration sensor or the speed sensor lies at any time before givingout an electrical stimulation and the measurement site staying still,for example, the components of gravity acceleration in the referencecoordinate system are [0, 1, 0], and the components of the gravityacceleration projected in the reference coordinate system are [0, 1,0]^(T).

The first subunit may acquire initial gravity components of the gravityacceleration at time t₀ in the initial coordinate system whencalculating the transition matrix from the reference coordinate systemto the kinetic coordinate system, where the time t₀ is any time beforegiving out the electrical stimulation and the measurement site stayingstill; then calculate the transition matrix from the referencecoordinate system to the initial coordinate system at time t₀ based onthe initial gravity components; calculate the transition matrix from theinitial coordinate system to the kinetic coordinate system based onangular velocity sampled values; and multiply the transition matrix fromthe reference coordinate system to the initial coordinate system by thetransition matrix from the initial coordinate system to the kineticcoordinate system to calculate the transition matrix from the referencecoordinate system to the kinetic coordinate system.

When calculating the transition matrix from the reference coordinatesystem to the initial coordinate system based on the initial gravitycomponents, the first subunit may calculate the rotation angles from theinitial coordinate system to the reference coordinate system based onthe initial gravity components, calculate the transition matrix from theinitial coordinate system to the reference coordinate system based onthe rotation angles from the initial coordinate system to the referencecoordinate system, and obtain the transition matrix from the referencecoordinate system to the initial coordinate system based on thetransition matrix from the initial coordinate system to the referencecoordinate system. When calculating the transition matrix from theinitial coordinate system to the kinetic coordinate system based onangular velocity sampled value, the first subunit may analyze theangular velocity sampled value to obtain rotation angles along themoving direction of an individual axis about the measurement site. In aspecific example, the rotation angles of the measurement site along themoving direction of an individual axis about the measurement site can beacquired by performing an integral operation, then calculating thevectors of motion state representing motion information about themeasurement site when it moves after it is stimulated according to therotation angles of a measurement site along the moving direction of anindividual axis about the measurement site, and acquiring the transitionmatrix from the initial coordinate system to the kinetic coordinatesystem based on the vectors of motion state. In a specific example, thevectors of motion state can be a quaternion, and the transition matrixfrom the initial coordinate system to the kinetic coordinate system canbe acquired based on the quaternion.

In the processing device for measuring the level of muscle relaxationprovided in the embodiment, the level of muscle relaxation can becalculated by sampled values of acceleration and angular velocityobtained by the acceleration sensor and the angular velocity sensor, andthe influence of the gravity acceleration to the measured result can beeliminated during calculation, which can improve the accuracy of themeasurement, so that the corresponding measuring device can be placed atany position of the measurement site without influencing the accuracy ofthe measured result.

The processor 201 can be one or more integrated chips recorded programswhich can be performed to achieve the above functions.

Though the present application has been described in detailed by way ofspecified examples, the examples are used for helping to appreciate thepresent application, not to limit the present application. Those skilledin the art can change the above specified embodiments based on thespirit of the present application.

What is claimed is:
 1. A method for measuring level of musclerelaxation, comprising: acquiring acceleration sampled values of ameasurement site from an acceleration sensor or a speed sensor;acquiring angular velocity sampled values of the measurement site froman angular velocity sensor; calculating components of gravityacceleration in an acceleration sensor coordinate system or a speedsensor coordinate system according to the acceleration sampled valuesand the angular velocity sampled values; subtracting the components ofgravity acceleration from the acceleration sampled values to obtainactual acceleration components in the acceleration sensor coordinatesystem or the speed sensor coordinate system; performing a compositionoperation on the actual acceleration components to obtain accelerationvalues generated by actual movement of the measurement site; andcalculating a level of muscle relaxation according to the accelerationsampled values and the angular velocity sampled values using theacceleration values identified by subtracting the components of gravityacceleration from the acceleration sampled values; the step ofcalculating components of gravity acceleration in an acceleration sensorcoordinate system or a speed sensor coordinate system according to theacceleration sampled values and the angular velocity sampled valuescomprises: calculating a transition matrix from a reference coordinatesystem to a kinetic coordinate system according to the accelerationsampled values from the acceleration sensor or the speed sensor and theangular velocity sampled values from the angular velocity sensor at timetk; where the time tk is any time after an electrical stimulation, thekinetic coordinate system is the acceleration sensor coordinate systemor the speed sensor coordinate system at the time tk, the referencecoordinate system is obtained by rotating an initial coordinate system,the initial coordinate system is the acceleration sensor coordinatesystem or the speed sensor coordinate system at any time before theelectrical stimulation and the measurement site staying still.
 2. Themethod for measuring level of muscle relaxation according to claim 1,wherein obtaining components of the gravity acceleration in theacceleration sensor coordinate system or the speed sensor coordinatesystem according to components of the gravity acceleration projected inthe reference coordinate system and the transition matrix from thereference coordinate system to the kinetic coordinate system.
 3. Themethod for measuring level of muscle relaxation according to claim 2,wherein the step of calculating a transition matrix from a referencecoordinate system to a kinetic coordinate system comprises: acquiringinitial components of gravity acceleration in the initial coordinatesystem at time t0 from the acceleration sensor or the speed sensor, thetime t0 is any time before the electrical stimulation and themeasurement site staying still; calculating a transition matrix from thereference coordinate system to the initial coordinate system at the timet0 based on the initial components of gravity acceleration; calculatinga transition matrix from the initial coordinate system to the kineticcoordinate system based on the angular velocity sampled values; andaccording to the transition matrix from the reference coordinate systemto the initial coordinate system and the transition matrix from theinitial coordinate system to the kinetic coordinate system, obtainingthe transition matrix from the reference coordinate system to thekinetic coordinate system.
 4. The method for measuring level of musclerelaxation according to claim 3, wherein the step of calculating atransition matrix from the reference coordinate system to the initialcoordinate system at the time t0 based on the initial components ofgravity acceleration comprises: calculating rotation angles from theinitial coordinate system to the reference coordinate system accordingto the initial components of gravity acceleration; calculating atransition matrix from the initial coordinate system to the referencecoordinate system according to the rotation angles; and obtaining thetransition matrix from the reference coordinate system to the initialcoordinate system according to the transition matrix from the initialcoordinate system to the reference coordinate system.
 5. The method formeasuring level of muscle relaxation according to claim 3, wherein thestep of calculating a transition matrix from the initial coordinatesystem to the kinetic coordinate system based on the angular velocitysampled values comprises: analyzing the angular velocity sampled valuesto obtain rotation angles along moving direction of individual axisabout the measurement site; obtaining vectors of motion state accordingto the rotation angles along moving direction of individual axis aboutthe measurement site, the vectors of motion state representing motioninformation about the measurement site when the part is moving after gotstimulated; and obtaining a transition matrix from the initialcoordinate system to the kinetic coordinate system according to thevectors of motion state.
 6. The method for measuring level of musclerelaxation according to claim 5, wherein the step of obtaining vectorsof motion state according to the rotation angles along moving directionof individual axis about the measurement site comprises: according tothe rotation angles along moving direction of individual axis about themeasurement site, obtaining the vectors of motion state with an inertialnavigation algorithm.
 7. A processing device for measuring musclerelaxation, comprising: a receiving unit for acquiring accelerationsampled values of a measurement site from an acceleration sensor or aspeed sensor, and for acquiring angular velocity sampled values of themeasurement site from an angular velocity sensor; and a processingmodule for calculating a level of muscle relaxation according to theacceleration sampled values and the angular velocity sampled values, theprocessing module further comprising: a gravity acceleration subtractionunit comprising a first subunit for calculating components of gravityacceleration in an acceleration sensor coordinate system or a speedsensor coordinate system according to the acceleration sampled valuesand the angular velocity sampled values, and a second subunit forsubtracting the components of gravity acceleration from the accelerationsampled values to obtain actual acceleration components in theacceleration sensor coordinate system or the speed sensor coordinatesystem; a composition unit for performing a composition operation on theactual acceleration components to obtain acceleration values generatedby actual movement of the measurement site; and a muscle relaxationcalculation unit for calculating the level of muscle relaxation based onthe acceleration values identified by subtracting the components ofgravity acceleration from the acceleration sampled values; wherein thegravity acceleration subtraction unit comprises: a first subunit forcalculating a transition matrix from a reference coordinate system to akinetic coordinate system according to the acceleration sampled valuesfrom the acceleration sensor or the speed sensor and the angularvelocity sampled values from the angular velocity sensor at time tk, andobtaining components of the gravity acceleration in the accelerationsensor coordinate system or the speed sensor coordinate system accordingto components of the gravity acceleration projected in the referencecoordinate system and the transition matrix from the referencecoordinate system to the kinetic coordinate system, where the time tk isany time after an electrical stimulation, the kinetic coordinate systemis the acceleration sensor coordinate system or the speed sensorcoordinate system at the time tk, the reference coordinate system isobtained by rotating an initial coordinate system, the initialcoordinate system is the acceleration sensor coordinate system or thespeed sensor coordinate system at any time before the electricalstimulation and the measurement site staying still.
 8. An apparatus formeasuring muscle relaxation, comprising: a constant-current source forgenerating stimulative current and through a current output thereof,applying current stimulation on a subject to be detected; aresponse-signal extraction end comprising an acceleration sensor and anangular velocity sensor or comprising a speed sensor and an angularvelocity sensor; and a processor connected with the constant-currentsource and communicatively coupled with the response signal extractionend for: controlling the constant-current source to generate stimulativecurrent; acquiring acceleration sampled values and angular velocitysampled values from motion information outputted by the response-signalextraction end; calculating components of gravity acceleration in anacceleration sensor coordinate system or a speed sensor coordinatesystem according to the acceleration sampled values and the angularvelocity sampled values; subtracting the components of gravityacceleration from the acceleration sampled values to obtain actualacceleration components in the acceleration sensor coordinate system orthe speed sensor coordinate system; performing a composition operationon the actual acceleration components to obtain acceleration valuesgenerated by actual movement of the measurement site; and calculating alevel of muscle relaxation according to the acceleration sampled valuesand the angular velocity sampled values using the acceleration valuesidentified by subtracting the components of gravity acceleration fromthe acceleration sampled values; wherein the processor calculatingcomponents of gravity acceleration in an acceleration sensor coordinatesystem or a speed sensor coordinate system according to the accelerationsampled values and the angular velocity sampled values comprises:calculating a transition matrix from a reference coordinate system to akinetic coordinate system according to the acceleration sampled valuesfrom the acceleration sensor or the speed sensor and the angularvelocity sampled values from the angular velocity sensor at time tk, andobtaining components of the gravity acceleration in the accelerationsensor coordinate system or the speed sensor coordinate system accordingto components of the gravity acceleration projected in the referencecoordinate system and the transition matrix from the referencecoordinate system to the kinetic coordinate system, where the time tk isany time after an electrical stimulation, the kinetic coordinate systemis the acceleration sensor coordinate system or the speed sensorcoordinate system at the time tk, the reference coordinate system isobtained by rotating an initial coordinate system, the initialcoordinate system is the acceleration sensor coordinate system or thespeed sensor coordinate system at any time before the electricalstimulation and the measurement site staying still.
 9. The apparatus formeasuring muscle relaxation according to claim 8, wherein the processorcalculating a transition matrix from a reference coordinate system to akinetic coordinate system according to the acceleration sampled valuesfrom the acceleration sensor or the speed sensor and the angularvelocity sampled values from the angular velocity sensor at time tkcomprises: acquiring initial components of gravity acceleration in theinitial coordinate system at time to from the acceleration sensor or thespeed sensor, the time to is any time before the electrical stimulationand the measurement site staying still; then calculating a transitionmatrix from the reference coordinate system to the initial coordinatesystem at the time to based on the initial components of gravityacceleration; calculating a transition matrix from the initialcoordinate system to the kinetic coordinate system based on the angularvelocity sampled values; and according to the transition matrix from thereference coordinate system to the initial coordinate system and thetransition matrix from the initial coordinate system to the kineticcoordinate system, obtaining the transition matrix from the referencecoordinate system to the kinetic coordinate system.
 10. The apparatusfor measuring muscle relaxation according to claim 9, wherein theprocessor calculating a transition matrix from the reference coordinatesystem to the initial coordinate system at the time t0 based on theinitial components of gravity acceleration comprises: calculatingrotation angles from the initial coordinate system to the referencecoordinate system according to the initial components of gravityacceleration, calculating a transition matrix from the initialcoordinate system to the reference coordinate system according to therotation angles and obtaining the transition matrix from the referencecoordinate system to the initial coordinate system according to thetransition matrix from the initial coordinate system to the referencecoordinate system; the processor calculating a transition matrix fromthe initial coordinate system to the kinetic coordinate system based onthe angular velocity sampled values comprises: analyzing the angularvelocity sampled values to obtain rotation angles along moving directionof individual axis about the measurement site, obtaining vectors ofmotion state according to the rotation angles along moving direction ofindividual axis about the measurement site, the vectors of motion staterepresenting motion information about the measurement site when the partis moving after got stimulated, and obtaining a transition matrix fromthe initial coordinate system to the kinetic coordinate system accordingto the vectors of motion state.